THE SIERRA DE ALVAREZ
October 20, 1996
Notes from a birding trip through Mexico by Jim Conrad
|At Mazatlán I take the
first long-haul bus I can back into the highlands, not at all sure where the next stop
will end up being. That afternoon as we pull out of Mazatlán first there are orchards and
fields right around town but it's not long until we're into the thornforest-covered
foothills of the Western Sierra Madres. The foothills fracture into ever more profoundly
broken landscape mantled with humid tropical deciduous forests and then we're passing
fabulous gorges like those around Témoris far to the north, and then oak-pine as at
Bahuichivo, and then chilly, high-elevation, pure pine forest as at Creel.
When we cross the state line from Sinaloa into Durango we dip onto the Interior High Plateau and cool, high-elevation desert, but this desert isn't as dry as what we've been through farther north. In the mountains above Durango City exactly at dusk I disembark the bus on a wild, windy, randomly chosen ridge far from any habitation and pitch my tent beneath an acacia gesturing hysterically in the wind
Next morning on an easy-going second-class bus I continue across a barren landscape that's cold, windswept, and dusty with occasional hang-dog towns and isolated ramshackle shacks. The open land is speckled with widely spaced mesquites and acacias, tree-size pricklypear cacti, tree yuccas, and rolling plains spreading between low, rust-colored, raw-looking ridges cleaved promiscuously with steep-banked, dried-up arroyos.
At longitude 23º27'N, at an elevation of about 2,100 meters (6,900 feet), on Highway 45 between Durango and Zacatecas, we cross the imaginary line around Earth exactly above which the sun takes it course once a year on the Summer Solstice, the first day of summer. This spot is announced by a rust-stained, wind-jiggled, open-arm-wide white sign with black lettering reading TROPICO DE CANCER. Now we technically enter the tropics, though from my seat in the rattletrap bus it looks and feels more like the chilly side of the Moon.
Late that night at the big bus station in the city of San Luis Potosí, I decide where my next stop needs to be, remembering it from visits made years ago when I came through here scouting the area for possible hikes to be included in a backpacking book. I buy a ticket to the hamlet of Xoconostle, thirty kilometers farther east (nineteen miles). Perched just below the peak, but on the western side of the Sierra de Alvarez, Xoconostle is a good place to go to experience the backbone of the Eastern Sierra Madres. In the Nahuatl language, the tongue of the ancient Aztecs still spoken by many Mexicans, xoconostle is the name of the pricklypear cactus's edible fruit.
MARÍA'S ORANGE FINCHES
Arriving in Xoconostle on a Sunday morning an hour after dawn, frost still whitens a few grassblades and loose chicken feathers on the ground. As the bus pulls away and I strap on the backpack, diminutive María López, an old woman keeping warm with a red shawl wrapped over her head and across most of her face in Moslem style, stands not far away looking at me. She operates a tiny roadside hole-in-the-wall selling softdrinks and crackers. From her I buy a couple of days' worth of carbohydrates.
María cannot suppress her questions. At my mention of birds her dark eyes peeping through the slit in the red shawl flush with pleasure. She asks me to follow her into the tiny courtyard behind her shack.
Two small, wire birdcages hang on the unfinished boards constituting her house's walls. One cage holds three birds, the other four. On the cages' floors are split-open pricklypear fruits, xoconostles, their pulpy flesh scarlet and glistening. Also there's alpiste -- freshly cut clusters of pods of a turniplike plant, the pods gorged with B-B-size seeds, and sold in Mexican markets as the preferred food for caged birds. María tells me each bird's name and history, says that such birds are very common in the desert around Xoconostle, that they sing beautifully, and then she asks me by what name such birds are called in English.
I am confused. Instantly my credibility as a gringo bird-specialist flies out the window.
From the short, thick bill it's easy to see that this is a kind of finch, but the males are pale orange, and I can't recall having ever seen anything orange in Mexico. I explain my astonishment, and bring out my bird book to show María that it must be closely related to strawberry-red House Finches, which I know very well, but these orange birds...
María laughs like a child and says that of course everybody knows that before these birds are caught they are then strawberry red. It's just that once they're caged up, they turn orange, and nobody knows why.
I take leave of María and begin hiking upward and eastward. The low, sparse, mostly spiny, cactus-rich vegetation along the road is indeed home to innumerable strawberry-red, male House Finches who sing their pretty, twittering melodies even on this cold morning in late October. It's sad to think about these birds fading once they're taken from the wild. However, it's hard to be angry with María for caging them.
She takes the best care of them she can, even feeding them xoconostles, which I know the birds love. I know this because Sahagún, the Spanish priest who during the 1500's wrote the history of the Aztecs, relates that the Aztecs also kept House Finches in cages, calling them by the name of nochtótotl, which meant "birds of the cactus fruits."
In the Western Sierra Madres, as a general rule, outcropping rock at ridge crests and along the faces of cliffs is igneous in origin. Millions of years ago molten lava erupted from volcanoes, or else bubbled up inside the earth to near the earth's surface, and then cooled to form the rock we see today. Perhaps the most common igneous rock outcropping in the Western Sierra Madres is basalt, which is very dark and fine-grained.
Much in contrast, here in the Eastern Sierra Madres, the typical outcropping rock is sedimentary, not igneous. It's mostly white limestone, not dark basalt. The limestone was deposited during the Cretaceous period some 100 to 135 million years ago, when dinosaurs roamed the earth's land masses, and a warm, shallow sea covered that part of the Earth now occupied by the Sierra de Alvarez, and most of the Eastern Sierra Madres.
Eventually I spot a ridge crest across a valley mantled with oak forest and there's not any kind of building anyplace around. I make my way there and find a fine camping spot near the ridge's crest where white limestone rock emerges from rusty-red clay. Before pegging the tent I go sit on a ledge admiring the valley below. After a while I lie back, turn onto my side, and notice that the limestone beneath me is made up of nothing but tiny shells of marine animals that died and sank to the ocean floor over a hundred million years ago.
Returning my gaze into the valley, for a long time I reflect on how hard it is to find anything that, upon closer examination, is not absolutely astounding.
Dried-out cow pads strew the ground all around camp so I'm not
surprised when right at dusk my descent into sleep is interrupted by sounds of snapping
twigs and heavy footsteps. I ignore my visitor until deep-breathing sounds come to right
outside my tent door and hot, clammy, grassy-odored breath fogs through the door's
mosquito netting into my face. Very slowly I turn over and look outside. Not an arm's
length away stands a bull with a massive head and horns as wide as my whole tent.
BORDERLINE CLOUD FOREST
The woods around the tent contains only a single species of oak, the exact identity of which I haven't the foggiest notion. The oaks are low, only reaching as high as the roof of a one-floor house. Small, leathery leaves cluster on outer branches so that inside each tree there's little more than a network of black, gnarled limbs bifurcating outward. Two-thirds of these branches' bark is blanketed with green moss and lichens. Among the lichens are a yellow-green, foliose species, and a bright orange fruticose species.
This accumulation of mosses and lichens on tree limbs isn't surprising. At this elevation -- some 2400 meters (7,920 feet) -- this ridge is a real barrier for wind. Humid wind blowing in from the Gulf rise up the eastern slopes coming to a peak right here, and as it does it cools. Since cool air holds less moisture than warm air of equal volume, its relative humidity automatically increases. If the rising air's relative humidity reaches the saturation point, it condenses into tiny water droplets.
Thus, often this very ridge is cloaked in mists and even when it isn't the air passing through its oaks is fairly moist. In such a humid environment, the gardens of mosses and lichens on these oaks' limbs need no roots reaching to the ground for water. They take what they need from the air.
This oak forest atop the Sierra de Alvarez is borderline cloudforest. If it were full-blown cloud forest, the masses of mosses and lichens would be even more spectacular.
MIXED FLOCK COMPARISON
At Lake Arareko we had a mixed-species flock. Here we have another flock, this one made up of different species. One flock has about ten Bushtits, three or four Rufous-capped Warblers, four Solitary Vireos, and one or two each of Nashville Warblers, Black-and-white Warblers, and Townsend's Warblers. Two Blue-headed Vireos sing as lustily as on any spring day up north, and a certain noisy Rufous-capped Warbler seems to be the leader or cheerleader in the same way a certain White-breasted Nuthatch was the leader at Lake Arareko.
At Lake Arareko, Brown Creepers and White-breasted Nuthatches gleaned tree bark. Here Black-and-white Warblers do that job. Like Williamson's Sapsuckers and Northern Flickers at Lake Arareko, who orbited around the flock's perimeter giving the impression that they were only casually part of the flock, here Hepatic Tanagers and Eastern Towhees do the same thing.
Of course, not all the birds here are groupies. In mid-afternoon quietness a lone Nashville Warbler comes working through the oaks methodically foraging for tiny arthropods along the oaks' branches and on their leathery leaves. Any time during the day the White-eared Hummingbird at the right might zip through. Everything about this in-between time of day feels sleepy and sluggish, but the little yellow warbler works at a fast pace with mechanical efficiency, with no wasted motions, no quick rests, and no perceivable changes in rhythm.
SEWING THE INDIAN WAY
Samalayuca's scorching sand converted my shoes to brittle cardboard, then climbing canyon walls at Bahuichivo and Témoris shattered them, leaving my toes poking through the sides and the shoes' heels flapping and snagging in grass. In Mazatlán I tried to buy new shoes but in Mexico, except in the largest cities, it's simply impossible to find my large size. Since I seem to have forgotten my sewing kit, today I sew my shoes "the Indian way."
At limestone ledges where oak forest gives way to white limestone outcrops, the most striking plant is the knee-high agave shown at the right, consisting of a bristling rosette of thick, succulent, leathery, sharp-pointed leaf-blades. More than once, looking for birds more than watching were I was going, spiny agave blade-tips have punctured my legs.
I cut a narrowly triangular blade-tip into a section about as long as the picture is high. The tip's cut base, about as thick as a finger, oozes a watery mucilage. Across the sliced face, embedded in yellow-green matrix material, it's easy to see cross sections of severed, stringlike veins feeding toward the black, bone-hard spine tip.
With a blunt woodchip I scrape the amputated section so that juice and pulpy green matter discharge from the cut face and the soft skin peels away. At first it's very messy but after ten minutes of scraping I'm left with a black awl firmly secured to about a dozen tough, threadlike fibers.
The agave-awl proves to be sharp and strong enough to pierce my shoes' rubbery soul and leather uppers. When the sewing is finished I'm very pleased with the improvement.
POLLINATION OF A SALVIA FLOWER
Among the most common herbs in this semiopen, limestone outcropping is a pretty, blue-flowered salvia, or sage, also about knee-high. In the afternoon I stand watching a mixed-species flock filter through the trees when the unmistakable whir of a hummingbird's wings materializes right below me, where the bird sips nectar at a profusely blossoming salvia. Very slowly I stoop. To my vast surprise the bird continues its work.
It's a female or immature Magnificent Hummingbird, called Rivoli's Hummingbird in some books, a species distinguished by its large size and the male's green throat and violet-blue crown. The bird before me is rather plain, but the conspicuous speckling on its pale throat and the shape and coloring of its tail assures my identification.
For a good two minutes the bird zips between blossoms, sometimes visiting flowers so low that the bird's tail practically touches the ground. When the bird is finished with all the blossoms its black bill's top is heavily daubed with white sage-pollen. Before the bird leaves it takes several stabs at gnats and other insects around us, so clearly Magnificent Hummingbirds are not strictly "nectiverous."
Once the show is over I dissect and sketch a salvia blossom so you can see the neat mechanism by which it delivers pollen to the bird's bill (the hummingbird is a White-eared, which also is here). As I sketch, an orange-yellow butterfly arrives also taking nectar from the blossoms. From what I can see, its slender proboscis does not at all activate the pollen-daubing mechanism shown at the right. Rather its proboscis snakes past the stamen filament's knobs and fulcrum attachments enabling the butterfly to take nectar without receiving pollen.
Here is this stop's Official List:
AT THE UNION OF TWO BIRD-WORLDS
Of all the birds listed at all the stops so far, not a single species has been one nesting exclusively in eastern North America. All of them have been either purely western birds or else they nested in both east and west. Today, here at the very peak of the eastern rim of the Mexican highlands we see our first mainly (not entirely) eastern North American species, the Black-and-white Warbler.
All this makes sense because Mexico's highlands are basically extensions of North America's western uplands, the Rockies. Mexico's hot, steamy Gulf lowland -- which lie at the foot of the slope beginning just a few kilometers east of here -- is an extension of eastern Texas's Coastal Plain, the same Coastal Plain that passes through Louisiana and extends northward via the Mississippi Embayment into southern Illinois and western Kentucky, and follows the US's Atlantic coast to New Jersey..
Thinking like this we can visualize two vast bird-zones fusing along the slope just the other side of this ridge on which I'm camped. If the teeming biology of Mexico's Gulf lowlands is an ocean, then the Black-and-white Warbler seen here is a smidgen of that ocean's spume splashed very high and a tiny bit onto the very shore of the highland realm of a geographic domain populated by bird species from western North American.
TO SANTA CATARINA
From the peak of Sierra Alvarez I catch a bus eastward, downslope to Santa Catarina, deeper into the domain of the Gulf Coast lowlands. Santa Catarina is a long, very narrow town of maybe a thousand, stretching along the Santa Catarina River. Here the highway's tortuous, steep descent abruptly changes to a much more easy-going one that slowly descends toward the Gulf. Though Santa Catarina lies 1,150 meters (3,800 feet) below the Sierra's peak, the elevation is still about 1,250 meters (4,100 feet), so at Santa Catarina we are only halfway into the lowlands.
On a footpath/livestock trail next to the river I follow the Santa Catarina River upstream, back into its canyon, fording the knee-deep stream again and again. At first cornfields and fenced-in pastures line the river but eventually they drop away. About an hour upstream it feels like wilderness again. I take a seat on a massive boulder rolled against the dark gray bark of an immense strangler-fig tree, and take account.
At 2 PM it's 31º C (88º F). The river here has narrowed to the point that I can pitch a stone across it. Its shallow waters scintillate in bright sunlight and breezes off the water feel fresh and playful. Though northerners would regard this as summer weather, trees along the stream are doing what their cousins up north are doing. Sycamores drop their dry, crispy, brown leaves while willows release into every breeze parachuted seeds that float in the air exploding with sunlight. On the rocky canyon walls many-armed garambula cactus rises house-high, cholla cactus stands high as an elephant, and tree-yuccas reach high as a second-story window.
Next morning, while working my way up a canyon, a metallic snapping sound causes me to turn and see a Greater Pewee, called Coue's Flycatcher in some books, with a Monarch Butterfly in its beak. For five minutes the pewee batters the butterfly against the dead snag it's perched on. Finally one of the butterfly's hindwings flutters to the ground. At this point the Pewee rears back its head and with jerking motions swallows the butterfly's remains. The Monarch's black body slides down easily but it takes about fifteen seconds for the orange and black wings to disappear. The whole episode astonishes me.
For one thing, the poor pewee is about as skinny and haggard looking as a living bird can be. Maybe it has a severe case of intestinal parasites or some other affliction. Moreover, I've never seen a bird work so hard to swallow anything. The impression is very clear that here is a starving bird eating something that normally it would avoid.
Also, Monarch Butterflies are famous for being so bitter that birds avoid eating them. Their flesh is permeated with noxious alkaloids from the milkweed plants Monarch caterpillars eat.
Once the Monarch is swallowed, the pewee wipes its bill on the snag twelve times and then preens it feathers for twenty minutes. This excessive bill wiping and feather preening suggests to me that the bird is trying to recover from an unsavory and unsettling experience.
Right now hundreds of Monarch Butterflies are sailing by. Some sail so high that they only show up in binoculars, but others pass within a meter of the disinterested pewee. The pewee's preening session ends only when a clear-winged, soft-bodied Mayfly-like insect wings by, for this is something more typical of a pewee's diet. This insect vanishes into the pewee in a fraction of a second.
In review, I first saw migrating Monarchs on September 21, in Kentucky. Then on October 6 a smaller number than this appeared at Samalayuca. The date on which I am seeing these great numbers in Santa Catarina is October 23. Many of the butterflies are faded and have tattered wings. It's easy to believe that they have come long distances.
If you're living the Mexican Dream in your little ranchito with a few orange and banana trees in the backyard and chickens scratching among the weeds, and you throw scraps to your chickens, Inca Doves will probably settle there once the chickens have gobbled the best morsels. Here Inca Doves appear along the trail paralleling the stream and on sandbars.
Bernardino de Sahagún, the Spanish priest who during the 1500's wrote the great history of central Mexico's Aztecs, reports that the Aztecs called Inca Doves cocotli, because the doves' cooing, to the Aztecs' ears, sounded like coco, coco. The Aztecs assured Sahagún that Inca Doves mate for life, and that when they make their sad cooing it's because one of the mates has died. Still, the Aztecs believed that eating the birds was therapeutic. Eating them drove away sadness and, in women, countered jealousy and caused them to forget about men.
Inca Doves don't live as far south as the land of the Inca in Peru but they do occupy an area from the southwestern U.S. to Costa Rica. They don't migrate but during recent times they've been expanding their range northward. In the U.S. they were first recorded only in southern Texas, south of San Antonio but I've seen them in southern Mississippi. The Inca Dove's feathers have dark borders, which give the bird a scaly appearance. Sometimes they are known as Scaled Doves.
In Mexico these little birds are famous for their fights. Sometimes the sound of buffeting wings can be heard two house-lengths from a battling pair. On the other hand, mated pairs of this species, as with most dove species, give the impression that they are excessively affectionate for one another because of their "billing and cooing."
BIRDLIST FOR CANYON ABOVE SANTA CATARINA
Here is this stop's Official List:
Go to Stop 8
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